<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <script>
        // 函数的定义
        function sum(a, b, c) {
            return a + b + c;
        }

        //第二种写法
        var sum2 = function(a, b, c) {
            return a + b + c;
        }

        // 箭头函数
        var sum3 = (a, b, c) => a + b + c;

        var fn = (x,y) => {
            let z = x + y;
            return z;
        }

    </script>
</body>
</html>